In this article we have attempted to make the case for continued participation by appropriately qualified mental health professionals in the adjudication of reconstructive subjective issues of the criminal law. In Part I, we outlined the reasons why imprecision and speculation is and must be tolerated in doctrines of exculpation and mitigation. In Part II, we developed the case for evidentiary rules which permit "informed speculation" by qualified clinical experts so as to enable defendants to explore and present subjective defenses and assist triers of fact to assess the plausibility and significance of such claims. We recognize that many mental health professionals have no special training or expertise in forensic matters and are not adequately sensitive to the risks of unreliability and imprecision in the evaluation process. We believe, accordingly, that the primary focus of reform should be on improving the quality of clinical participation in the criminal process, an effort which depends primarily on collaboration between the bar and the mental health professions to define the necessary qualifications of expert witnesses and to establish criteria for acceptable evaluation procedures. We sought in Part III to contribute to this collaborative effort by outlining some general guidelines that might facilitate objectivity in forensic evaluation